1. Field of the Invention
The invention relates to safety syringes in general and to blood collection safety syringes in particular.
2. Prior Art
The risk of contracting diseases such as HIV or hepatitis from accidental sticks with dirty needles is a potentially deadly hazard for medical professionals. One of the most dangerous times for accidental sticks is during blood collection. This is frequently done with a syringe and one or more vacuum specimen tubes. These syringes are typically comprised of a hollow shroud having an open end and a closed end. A double pointed hollow needle is usually threaded into the closed end of the shroud such that one end of the needle is positioned outside of the shroud and the other end of the needle is positioned inside the shroud. Both ends of the needle are usually sharp. The end of the needle that is inside the shroud is usually covered with a collapsible latex sleeve which seals the end of the needle.
The vacuum specimen tubes are essentially test tubes sealed with a rubber stopper. These tubes are usually sealed under a vacuum but in their principal intended use, they only require a pressure that is lower than the venous pressure of the patient in order to draw blood. Thus, as used herein the term xe2x80x9cvacuum specimen tubexe2x80x9d refers to sealed tubes having an internal pressure that is less than the venous pressure of the patient.
In operation, the external end of the needle is injected into the patient, usually into a vein. At this point, the collapsible sleeve prevents blood from flowing out of the needle. A vacuum specimen tube will then be inserted into the open end of the shroud until the rubber stopper encounters the internal end of the needle. Continued application of pressure to the vacuum specimen tube will cause the sharp point of the internal end of the needle to pierce the collapsible sleeve and enter the rubber stopper. When the stopper has been completely pierced, the needle will provide fluid passage between the vein and the vacuum specimen tube. The difference in pressure between the tube and the vein will cause blood to flow into the tube until the pressure is equalized. When this happens, the tube will usually be removed while the needle is still in the patient. The sleeve will snap back into place when the tube is removed. Even though the sleeve has been pierced, it is resilient enough to prevent blood from escaping while the tube is out of place. If more blood is required, a fresh tube may be placed onto the internal end of the needle. This is repeated until the desired amount of blood has been collected.
When the last tube has been filled, the needle is removed from the patient. At this time, the needle is dirty and exposed and an accidental stick is possible from this point on. This may occur while the medical professional is removing the last tube from the syringe or while she is disposing the syringe. Also, personnel handling medical refuse may be stuck after the syringe has been discarded.
The foregoing description assumes that the patient is well behaved and that blood is drawn in a careful and orderly fashion. All too frequently, this is not the case. In many emergency room settings, such as trauma or overdose cases, the patient may be violent, and he may need to be restrained in order for blood to be drawn. Children may also behave uncontrollably during blood collection. Such activity on the part of the patient obviously increases the risk of an accidental stick. It also changes the time when protection is required. In a case where the patient is orderly and all goes well, protection from an accidental stick is not needed until after blood collection is complete. Where the patient is disorderly, protection is required during the collection procedure.
Protection during the collection procedure is also beneficial for the patient. He is exposed to potential injury while the sharp needle is in his vein. If the patient becomes agitated, his movements may cause the needle to damage the vein or the surrounding tissue. Even if the patient is still, the movement of the syringe by the medical professional as she is changing tube may cause damage to the vein. Accordingly, a safety syringe that meets the following objectives is desired.
It is an object of the invention to help prevent the transmission of AIDS and other diseases through accidental sticks with contaminated needles.
It is an object of the invention to provide a safety syringe which minimizes the chances of an accidental stick with a contaminated needle.
It is an object of the invention to provide a safety syringe which minimizes the risk of damage to the veins of the patient.
It is an object of the invention to provide a safety syringe capable of collecting blood and other fluids.
It is another object of the invention to provide a safety syringe in which the needle is covered prior to its removal from the patient.
It is yet another object of the invention to provide a safety syringe in which the sheath is locked into place when the needle is covered.
It is still another object of the invention to provide a safety syringe that operates in a substantially similar fashion to a conventional blood collection syringe.
The invention is a safety syringe for collecting fluids in a vacuum specimen tube. The syringe comprises a shroud having a first end, a second end, and sidewalls extending therebetween, all of which define a shroud chamber. The second end is preferably open to provide access to the shroud chamber. The shroud chamber is sized to receive a vacuum specimen tube. A needle having a first end and a second end is mounted in the first end of the shroud such that the first end of the needle is outside of the shroud and the second end of the needle is positioned within the shroud chamber. A blunt sheath having a tip end is slidably disposed over the needle. Preferably, at least the tip end of the sheath is sized to be hypodermically inserted with the first end of the needle. The sheath has a covered position in which the point of the first end of the needle is contained within the sheath. The sheath also has an exposed position in which the point of the first end of the needle is outside of the sheath. The sheath is configured to advance from the exposed position to the covered position by sliding along the needle. Preferably, an arm extends from the sheath to within the shroud chamber. This arm has a tube end opposite the sheath. As the vacuum specimen tube is advanced toward the first end of the needle, the tube will engage the tube end of the arm and push it forward. This will cause the sheath to move from the exposed position to the covered position. This is preferably accomplished immediately after the needle has been inserted into the patient, so that the needle is in the covered position throughout most of the fluid collection procedure, and substantially all the time the needle is dirty.
As the vacuum specimen tube is advanced toward the first end of the shroud, it will also encounter the second end of the needle. The second end of the needle is configured to pierce the stopper sealing the vacuum specimen tube, preferably with a sharp point identical to that of the first end of the needle. When the second end has pierced the stopper, the needle will provide fluid passage into the vacuum specimen tube. At this point, the first end of the needle should already be in the vein or other vessel. If so, the vacuum of the tube will cause fluid to flow through the needle into the tube. When the vacuum specimen tube is full, it may be removed and another added until the desired amount of blood or other fluid has been collected. When the collection is complete and the syringe is removed, it will already be in the covered position.